It is known in the area of internal combustion engine emissions control that the time during which an engine is running prior to the certain emissions control components reaching critical operating temperatures is a significant contributor to overall hydrocarbon tailpipe emissions. This is generally true because the catalysts used to treat exhaust gases are inefficient at lower temperatures and because the exhaust gas sensors used for closing the loop on air-fuel ratio have not yet reached their operating temperature and thus cannot be used. Additionally, the engine is typically calibrated with rich air-fuel ratios to avoid misfires and partial burns, which further contributes to the hydrocarbon emissions. It is also generally well understood that tailpipe emissions during cold starts can be significantly reduced if the time for such components to reach acceptable performance temperatures can be reduced.
There are known systems that rely upon air injection reaction pumps for feeding air into the exhaust for post combustion hydrocarbon combustion and heat generation upstream of the catalytic converter. Such systems come with expense, mass and reliability penalties.
In attempting to address these needs and shortfalls, approaches have been proposed for reducing the time it takes to reach critical temperatures. It is known that increasing the engine speed increases the thermal output to the exhaust and can effect a reduction in the time for exhaust components to reach these critical temperatures. However, excessively high engine speeds may be objectionable to a vehicle operator. It is also known that retarding the spark timing serves to increase the thermal energy transported to the exhaust system. However, modern engines have limited spark retard authority as too much retard contributes to combustion instability.
It is also known that increasing the engine load and thus the amount of fuel consumed per combustion cycle also increases the heat output to the exhaust. Systems have been proposed for increasing engine load by overexciting a vehicle starter/alternator in combination with spark retard and fuel enleanment. No teaching is given of what is meant by overexciting the starter/alternator and no teaching is given to indicate where the additional energy is dissipated. However, such an arrangement suggests energy dissipation internal to the machine, which may mean unregulated operation and damaging voltage/current levels. This represents a potentially damaging or wasteful energy dump.
Electrically heated catalysts have also been proposed as a means for accelerating the heating of the catalyst. Such systems demand significant electrical energy to effect rapid heating. Energizing electrically heated catalysts for direct heating thereof has been proposed by disconnection of normal vehicle electrical loads from the generator and generator operation in an unregulated mode to rapidly power such a catalyst heater.